1. Field of the Invention
The present invention relates to an electro-photographic typed image forming device provided in a facsimile machine, a copy machine or the like.
2. Description of the Related Art
There is an electro-photographic typed image forming device which includes a photoconductive drum driven by a rotation driving mechanism, a charging unit which charges the photoconductive drum, an exposing unit which writes image information as an electrostatic latent image onto the charged photoconductive drum, a developing unit which develops the electrostatic latent image formed by the exposing unit, a transfer unit which transfers the developed image onto a recording medium, and a paper dust removing unit which contacts against the surface of the photoconductive drum to remove paper dust.
In the above-mentioned image forming device, a positive charging process that positively charges the surface of the photoconductive drum has been drawing attention recently.
When carrying out a corona charging process, in case of a negative corona discharge, ozone is generated, and in case of a positive corona discharge, ozone is not generated. Therefore, under the positive charging process, a corona discharging typed charging unit can be used, and the surface of the photoconductive drum can be charged uniformly under low cost. Moreover, a positively charged toner suitable for the positive charging process is being developed to be put into practical use.
However, paper dust is prone to be charged negatively. Therefore, when transferring an image onto paper, there are cases when the paper dust adhere to the positively charged surface of the photoconductive drum to cause a failure in charging or white spots. To avoid such a problem, it is necessary to provide a brush for removing the paper dust. When a fixed brush is used for the brush, the duration of the brush is shorter than the duration of the drum. Therefore, when the brush for removing the paper dust and the photoconductive drum are formed as one unit, the duration of the unit is determined by the duration of the brush for removing the paper dust. As a result, a photoconductive drum which can be still used is abandoned.
As a countermeasure, there is a proposal to form the brush for removing the paper dust as a rotating brush. However, in this case, a process to remove the paper dust by contacting a flicker against the brush becomes necessary, and it also becomes necessary to provide a space for accumulating the removed paper dust.